1. Field of the Invention:
The present invention relates to the heat treatment of products comprising a thermally insulating material, particularly with a view to bringing about polymerisation and/or polycondensation reactions of certain components within the substance of the product.
It relates to a process and apparatus for heating by dielectric loss under ultra-high frequency radiation, particularly suitable for application to the treatment of felts or products based on mineral fibre felts, in particular in the form of shaped pieces such as insulating shells.
2. Background of the Prior Art:
It is known that insulating shells are conventionally manufactured by winding a certain number of superimposed layers of a mat of mineral fibres impregnated with a thermosetting resin around a mandrel, the definitive form of the object being fixed by a heat treatment.
The heat treatment hitherto carried out generally consists of applying a blast of hot air from the interior of the shell if the shell has a large diameter or from the outside in the case of a shell of small diameter, the shell being in that case heated by conduction from the outside to the inside. Such a method of treatment has been described, for example, in French Patent No. FR-A-2 325 007.
This technique usually has the disadvantage of being relatively expensive in energy consumption and slow since it requires the previous removal of residual water left in the material from various preliminary operations such as the formation and impregnation of the fibrous mat.